U.S. patent application number 16/641131 was filed with the patent office on 2020-07-30 for display apparatus and method of controlling the same.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. The applicant listed for this patent is SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Tae Gyoung AHN, Dong Yoon KIM, Sang Hun KIM, Young Su MOON, Seung-Ho PARK, Ho Cheon WEY.
Application Number | 20200245000 16/641131 |
Document ID | 20200245000 / US20200245000 |
Family ID | 1000004766606 |
Filed Date | 2020-07-30 |
Patent Application | download [pdf] |
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United States Patent
Application |
20200245000 |
Kind Code |
A1 |
KIM; Dong Yoon ; et
al. |
July 30, 2020 |
DISPLAY APPARATUS AND METHOD OF CONTROLLING THE SAME
Abstract
A display apparatus and method that reduces block noise by
performing block noise boundary detections and generating a block
noise boundary map on the basis of a result of the detections to
cope with local random block noise having irregular shaped and
blurred block boundaries to perform adaptive deblocking filtering.
The apparatus includes: an image receiver; a map generator to
generate a block boundary map by performing convolution using a
plurality of kernels on a received image; a determiner to determine
a filter parameter on the basis of the block boundary map and a
block boundary period included in the block boundary map; a
deblocking filter to vary a filter strength on the basis of the
determined filter parameter; and a display on which an image in
which block noise is removed by the deblocking filter is
displayed.
Inventors: |
KIM; Dong Yoon; (Suwon-si,
KR) ; PARK; Seung-Ho; (Suwon-st, KR) ; AHN;
Tae Gyoung; (Suwon-si, KR) ; WEY; Ho Cheon;
(Suwon-si, KR) ; KIM; Sang Hun; (Suwon-si, KR)
; MOON; Young Su; (Suwon-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAMSUNG ELECTRONICS CO., LTD. |
Suwon-si |
|
KR |
|
|
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Suwon-si
KR
|
Family ID: |
1000004766606 |
Appl. No.: |
16/641131 |
Filed: |
December 7, 2018 |
PCT Filed: |
December 7, 2018 |
PCT NO: |
PCT/KR2018/015540 |
371 Date: |
April 10, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04N 5/23293 20130101;
H04N 19/895 20141101; H04N 5/23229 20130101 |
International
Class: |
H04N 19/895 20060101
H04N019/895; H04N 5/232 20060101 H04N005/232 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 8, 2017 |
KR |
10-2017-0168084 |
Claims
1. A display apparatus comprising: an image receiver configured to
receive an image; a block boundary map generator configured to
generate a block boundary map by performing convolution using a
plurality of kernels on the image received from the image receiver;
a filter parameter determiner configured to determine a filter
parameter on the basis of the block boundary map and a block
boundary period included in the block boundary map; a deblocking
filter configured to vary a filter strength on the basis of the
determined filter parameter; and a display on which an image in
which block noise is removed by the deblocking filter is
displayed.
2. The display apparatus of claim 1, wherein the block boundary map
generator generates a first block boundary map by comparing
correlation values obtained by performing the convolution using the
plurality of kernels with a predetermined reference value, and
generates a second block boundary map by correcting the first block
boundary map on the basis of c of a block boundary included in the
first block boundary map.
3. The display apparatus of claim 2, wherein the block boundary map
generator calculates a histogram obtained by accumulating a number
of block boundaries included in the second block boundary map,
calculates an average block edge strength on the basis of the
histogram, and determines the block boundary period on the basis of
the average block edge strength and a predetermined reference
value.
4. The display apparatus of claim 3, wherein the block boundary map
generator generates a third block boundary map by correcting the
second block boundary map on the basis of the determined block
boundary period.
5. The display apparatus of claim 4, wherein the filter parameter
determiner determines the filter parameter on the basis of at least
one of the average block edge strength, the block boundary period,
a reliability of the block boundary period, or a block edge
strength included in the third block boundary map.
6. The display apparatus of claim 5, wherein the deblocking filter
adjusts the filter strength to be proportional to the block
boundary period or the magnitude of the average block edge
strength.
7. The display apparatus of claim 1, wherein the block boundary map
generator performs normalization on the image received from the
image receiver,
8. The display apparatus of claim 2, wherein the block boundary map
generator generates a plurality of correlation maps on the basis of
the correlation values, and generates the first block boundary map
on the basis of locations of selected pixels in the plurality of
correlation maps.
9. The display apparatus of claim 8, wherein the first block
boundary map includes a two-directional map generated in a
horizontal direction and a vertical direction.
10. The display apparatus of claim 1, wherein the block boundary
map generator determines the block boundary period on the basis of
an offset when the input image includes a letter box.
11. A method of controlling a display apparatus, the method
comprising: receiving an image; generating a block boundary map by
performing convolution using a plurality of kernels on the image;
determining a filter parameter on the basis of the block boundary
map and a block boundary period included in the block boundary map;
performing deblocking filtering by varying a filter strength on the
basis of the determined filter parameter; and displaying a result
of the filtering.
12. The method of claim 11 wherein the generating of the block
boundary map includes: generating the block boundary map by
comparing correlation values obtained by performing convolution
using the plurality of kernels with a predetermined reference
value, and correcting the block boundary map on the basis of
continuity of a block boundary included in the block boundary
map.
13. The method of claim 12, wherein the correcting of the block
boundary map includes: calculating a histogram obtained by
accumulating a number- of block boundaries included in the
generated block boundary map; and determining the block boundary
period on the basis of the average block edge strength and a
predetermined reference value.
14. The method of claim 13, wherein the correcting of the block
boundary map includes correcting the corrected block boundary map
on the basis of the determined block boundary period,
15. The method of claim 14, wherein the determining of the filter
parameter includes determining the filter parameter on the basis of
at least one of the block boundary period, a reliability of the
block boundary period, or a block edge strength included in the
third block boundary map.
16.-19. (canceled)
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a display apparatus
capable of removing block noise occurring in a compressed image and
a method of controlling the same.
BACKGROUND ART
[0002] A display apparatus is an output device that converts
acquired or stored electrical information into visual information
and displays the visual information to a user. In addition, the
display apparatus may perform predetermined image processing on a
received or stored image, and display the processed image to a
user.
[0003] With recent improvement in the performance of cameras,
moving images come to have a higher resolution. However, when a
produced image is compressed and transmitted, block noise may occur
in the process of image processing due to the limited transmission
bandwidth.
[0004] With development of technology for compressing moving
images, the block noise also comes in different shapes. For
example, compression codecs prior to MPEG-4 generate block noise in
regular shapes and sizes. However, recent H-264 or H-265 coding
schemes generate block noises in irregular and various shapes.
[0005] In the H-264 or H-265 coding scheme, block noise boundaries
may be blurred by deblocking filtering. In addition, even when an
image encoded with H-264 or H-265 is upscaled at an outside of the
display apparatus, block noise boundaries may be blurred.
Accordingly, there is a need for a method of detecting blurred
block noise boundaries.
[0006] The conventional technologies for removing the above
described constraints have the following technical features and
limitations.
[0007] Related art 1 (U.S. Registered Patent No.: U.S. Pat. No.
7,865,035) discloses a technique of receiving video parameter
information from a decoder, analyzing image quality, and adjusting
the filter strength on the basis of information about the image
quality. However, since related art 1 receives information for
analyzing the image quality from the decoder, and thus has
difficulty in coping with an input of a blind image, information of
which is unclear.
[0008] Related art 2 (U.S. Registered Patent No.: U.S. Pat. No.
7,911,538) discloses a technique of calculating the strength of
block noise using edge ratio, edge value, and edge count, and
performing deblocking filtering on the basis of the calculated
strength. However, Related art 2 has a low accuracy due to a large
amount of general edge information.
[0009] (Patent Document 1) U.S. Pat. No. 7,865,035 B2
[0010] (Patent Document 2) U.S. Pat. No. 7,911,538 B2
DISCLOSURE
Technical Problem
[0011] The present disclosure provides a display apparatus that is
improved to reduce block noise by performing a plurality of block
noise boundary detections and generating a block noise boundary map
on the basis of a result of the detections to cope with local
random block noise having irregular shaped and blurred block
boundaries so that adaptive deblocking filtering is performed, and
a method of controlling the same.
Technical Solution
[0012] According to an aspect of the present disclosure, there is
provided a display apparatus including: an image receiver
configured to receive an image; a block boundary map generator
configured to generate a block boundary map by performing
convolution using a plurality of kernels on the image received from
the image receiver; a filter parameter determiner configured to
determine a filter parameter on the basis of the block boundary map
and a block boundary period included in the block boundary map; a
deblocking filter configured to vary a filter strength on the basis
of the determined filter parameter; and a display on which an image
in which block noise is removed by the deblocking filter is
displayed.
[0013] The block boundary map generator may generate a first block
boundary map by comparing correlation values obtained by performing
the convolution using the plurality of kernels with a predetermined
reference value, and generate a second block boundary map by
correcting the first block boundary map on the basis of continuity
of a block boundary included in the first block boundary map.
[0014] The block boundary map generator may calculate a histogram
obtained by accumulating a number of block boundaries included in
the second block boundary map, calculate an average block edge
strength on the basis of the histogram, and determine the block
boundary period on the basis of the average block edge strength and
a predetermined reference value.
[0015] The block boundary map generator may generate a third block
boundary map by correcting the second block boundary map on the
basis of the determined block boundary period.
[0016] The filter parameter determiner may determine the filter
parameter on the basis of at least one of the average block edge
strength, the block boundary period, a reliability of the block
boundary period, or a block edge strength included in the third
block boundary map.
[0017] The deblocking filter may adjust the filter strength to be
proportional to the block boundary period or the magnitude of the
average block edge strength.
[0018] The block boundary map generator may perform normalization
on the image received from the image receiver.
[0019] The block boundary map generator may generate a plurality of
correlation maps on the basis of the correlation values, and
generate the first block boundary map on the basis of locations of
selected pixels in the plurality of correlation maps.
[0020] The first block boundary map may include a two-directional
map generated in a horizontal direction and a vertical
direction.
[0021] The block boundary map generator may determine the block
boundary period on the basis of an offset when the input image
includes a letter box.
[0022] According to another aspect of the present disclosure, there
is provided a method of controlling a display apparatus, the method
including: receiving an image; generating a block boundary map by
performing convolution using a plurality of kernels on the image;
determining a filter parameter on the basis of the block boundary
map and a block boundary period included in the block boundary map;
performing deblocking filtering by varying a filter strength on the
basis of the determined filter parameter; and displaying a result
of the filtering.
[0023] The generating of the block boundary map may include:
generating the block boundary map by comparing correlation values
obtained by performing convolution using the plurality of kernels
with a predetermined reference value, and correcting the block
boundary map on the basis of continuity of a block boundary
included in the block boundary map.
[0024] The correcting of the block boundary map may include:
calculating a histogram obtained by accumulating a number of block
boundaries included in the generated block boundary map; and
determining the block boundary period on the basis of the average
block edge strength and a predetermined reference value.
[0025] The correcting of the block boundary map includes correcting
the corrected block boundary map on the basis of the determined
block boundary period.
[0026] The determining of the filter parameter may include
determining the filter parameter on the basis of at least one of
the block boundary period, a reliability of the block boundary
period, or a block edge strength included in the third block
boundary map.
[0027] The performing of deblocking may include adjusting the
filter strength to be proportional to the block boundary period or
the magnitude of the average block edge strength.
[0028] The generating of the block boundary map may include
performing normalization on the image.
[0029] The generating of the block boundary map may include
generating a plurality of correlation maps on the basis of the
correlation values, and generating the block boundary map on the
basis of a location of a selected pixel in the plurality of
correlation maps.
[0030] The generating of the block boundary map may include
determining the block boundary period on the basis of an offset
when the input image includes a letter box.
Advantageous Effects
[0031] According to the above-described aspects of the present
disclosure, the display apparatus and the method of controlling the
same can more effectively reduce block noise compared to the
conventional technology by performing a plurality of block noise
boundary detections and generating a block noise boundary map on
the basis of a result of the detections to cope with local random
block noise having irregular block shapes and blurred block
boundaries so that adaptive deblocking filtering is performed
DESCRIPTION OF DRAWINGS
[0032] FIG. 1 is a diagram illustrating a configuration in which an
image is transmitted to a display apparatus according to an
embodiment.
[0033] FIG. 2 is a control block diagram illustrating a display
apparatus according to an embodiment.
[0034] FIG. 3 is a flowchart showing a method of controlling a
display apparatus according to an embodiment.
[0035] FIG. 4 is a flowchart showing a method of generating a first
block boundary map described in FIG. 3.
[0036] FIGS. 5 to 11 are detailed views for describing the method
shown in FIG. 4.
[0037] FIG. 12 is a flowchart showing a method of correcting a
generated block boundary map.
[0038] FIGS. 13A and 13B are views for describing a method of
determining a block boundary period.
[0039] FIGS. 14A to 13D are views illustrating a process of
detecting a block boundary according to an example.
[0040] FIG. 15 is a detailed flowchart for describing a control
method of determining a filter parameter and performing deblocking
filtering according to an embodiment.
[0041] FIGS. 16A to 16C are views for describing a block boundary
detection effect according to an embodiment.
[0042] FIGS. 17A to 17C are views for comparing the block noise
reduction according to the disclosure.
MODE FOR DISCLOSURE
[0043] Like numerals refer to like elements throughout the
specification. Not all elements of embodiments of the present
disclosure will be described, and description of what are commonly
known in the art or what overlap each other in the embodiments will
be omitted. The terms as used throughout the specification, such as
".about.part", ".about.module", ".about.member", ".about.block",
etc., may be implemented in software and/or hardware, and a
plurality of ".about.parts", ".about.modules", ".about.members", or
".about.blocks" may be implemented in a single element, or a single
".about.part", ".about.module", ".about.member", or ".about.block"
may include a plurality of elements.
[0044] It will be further understood that the term "connect" or its
derivatives refer both to direct and indirect connection, and the
indirect connection includes a connection over a wireless
communication network.
[0045] It will be further understood that the terms "comprises"
and/or "comprising," when used in this specification, specify the
presence of stated features, integers, steps, operations, elements,
and/or components, but do not preclude the presence or addition of
one or more other features, integers, steps, operations, elements,
components, and/or groups thereof, unless the context clearly
indicates otherwise.
[0046] Although the terms "first," "second," "A," "B," etc. may be
used to describe various components, the terms do not limit the
corresponding components, but are used only for the purpose of
distinguishing one component from another component.
[0047] As used herein, the singular forms "a," "an" and "the" are
intended to include the plural forms as well, unless the context
clearly indicates otherwise.
[0048] Reference numerals used for method steps are just used for
convenience of explanation, but not to limit an order of the steps.
Thus, unless the context clearly dictates otherwise, the written
order may be practiced otherwise.
[0049] Hereinafter, the operating principles and embodiments of the
present disclosure will be described with reference to the
accompanying drawings.
[0050] FIG. 1 is a diagram illustrating a configuration in which an
image is transmitted to a display apparatus 100 according to an
embodiment.
[0051] Referring to FIG. 1, the display apparatus 100 may receive a
compressed or decompressed image from an image provider 10.
[0052] The display apparatus 100 refers to an output device capable
of providing an image to a user. To this end, the display apparatus
100 may be provided with a processor, such as a central processing
unit (CPU) or a micro control unit (MCU) that is required for
processing an image and performing functions.
[0053] Referring to FIG. 1, the display apparatus 100 may include a
television apparatus 100a, a portable terminal apparatus 100b, or a
computer apparatus 100c, such as a personal computer or a server
computer.
[0054] Meanwhile, the display apparatus 100 may display a still
image or a moving image to a user using various types of display
device. The display device may be variously implemented using a
cathode ray tube, a cold cathode fluorescent lamp, a light emitting
diode, an organic light emitting diode, an active-matrix organic
light emitting diode, liquid crystals, electronic paper, or the
like.
[0055] In addition, the display apparatus 100 may output sound to
the user at the same time of reproducing an image.
[0056] The image provider 10 refers to a provider that transmits a
stored or generated image and/or sound to the display apparatus 100
in the form of data. Referring to FIG. 1, the image provider 10 may
include a broadcast transmission apparatus 10a, a server apparatus
10b, or an external storage medium 10c detachable from the
television apparatus 100a.
[0057] The broadcast transmission apparatus 10a is provided to
transmit image data and/or sound data to the display apparatus 100
using electromagnetic waves of a predetermined frequency band for
public transmission.
[0058] The server apparatus 10b is provided to transmit image data
and/or sound data to the display apparatus 100 through a wireless
network or a wired network. Here, the wired communication network
may be a network constructed using a cable, such as a pair cable, a
coaxial cable, a fiber optic cable, an Ethernet cable, or the like.
The wireless network may be a network implemented using short range
communication standards or mobile communication standards. The
wireless network using the short range communication standards may
be is implemented using wireless communication technology, such as
Wi-Fi, Bluetooth, zigbee, Wi-Fi Direct (WFD), ultra wideband (UWB),
infrared data association (IrDA), bluetooth low energy (BLE), near
field communication, and the like. The wireless network using the
mobile communication standards may be classified into 3GPP series
wireless communication technology, such as evolutionary high speed
packet access (HPDA+) or long term evolution (LTE), 3GPP2 series
wireless communication technology, such as optimized evolution-data
(EV-Do), or WiMAX series wireless communication technology, such as
WiBro Evolution.
[0059] The external storage medium 10c may store various types of
data and may transmit image to the display apparatus 100 by being
directly coupled to the display apparatus 100 or may transmit or
provide image data to the display apparatus 100 using a cable or a
wireless network, as in an external hard disk or a universal serial
bus (USB) memory device.
[0060] The image provider 10 according to the embodiment compresses
a produced image before providing the image to the display
apparatus 100. The display apparatus 100 receiving the compressed
image decodes the compressed image and outputs the decoded
image.
[0061] However, the compressed image transmitted by the image
provider 10 may have an irregular block shape, and block noise in
which block boundaries are blurred by in-loop deblocking
filtering.
[0062] As another example, when a set-top box rescales a
low-resolution image and provides the image to the television
apparatus 100a, the provided image may have blurring block noise,
including block noise with irregular block sizes and blurred block
boundaries.
[0063] The display apparatus 100 and the method of controlling the
same may provide an improved image to a user by detecting and
removing block noise that are generated in irregular forms.
[0064] FIG. 2 is a control block diagram illustrating a display
apparatus according to an embodiment.
[0065] Referring to FIG. 2, the display apparatus 100 includes an
image receiver 110 for receiving an image transmitted by the image
provider 10 and decompressing the received image, an image
processor 130 for detecting block boundaries in the received image
and performing deblocking filtering, a storage 150 for storing the
provided image and various types of data, and a display 170 for
outputting the image in which block noise is removed.
[0066] In detail, the image receiver 110 may receive an image that
is decompressed by the image processor 10 from the outside of the
display apparatus 100. Alternatively, the image receiver 110 may
decompress an image, which has been received without being
decompressed, using a decoder.
[0067] For example, the image receiver 110 decodes an image that is
compressed by the H-264 or H-265 codec. However, the image receiver
110 according to the present disclosure is not limited thereto, and
may be implemented as various decoding modules as long as it can
decompress an image and generate irregular block boundaries and
blurred blocks.
[0068] The image processor 130 is configured to remove irregular
block noise. The image processor 130 may include a block boundary
map generator 131 for generating a block boundary map on the basis
of a block boundary existing in a received image, a filter
parameter determiner 133 for determining a parameter with which
adaptive deblocking filtering is performed, and a deblocking filter
135 for performing deblocking on the basis of the determined
parameter. First, the block boundary map generator 131 performs
convolution using a plurality of kernels corresponding to irregular
and various forms of blocks, and generates an initial block
boundary map (hereinafter, referred to as a first block boundary
map) on the basis of a result value of the convolution
(hereinafter, referred to as a correlation value).
[0069] In addition, the block boundary map generator 131 uses a
histogram to determine an interval between block boundaries
(hereinafter, referred to as a block boundary period). In other
words, the block boundary map generator 131 determines the block
boundary period by comparing a block edge strength calculated on
the basis of the histogram with a predetermined threshold
value.
[0070] The block boundary map generator 131 may generate a final
block boundary map by correcting the first block boundary map on
the basis of the determined block boundary period.
[0071] The filter parameter determiner 133 may determine a filter
parameter that is applied to deblocking, on the basis of at least
one of a final block boundary map and an average block edge
strength calculated during generation of the final block boundary
map, a reliability calculated from the histogram, a block edge
strength, or a block boundary period.
[0072] In detail, the filter parameters may be classified into a
global filter parameter in a frame and a local filter parameter
applied to a block of each image. The global parameter may be
determined on the basis of at least one of an average block edge
strength and a reliability calculated in a histogram. In addition,
the local parameter may be determined on the basis of at least one
of a reliability calculated from a histogram, a block edge
strength, or a block boundary period.
[0073] Factors required for determining the filter parameters may
be described below in detail with reference to other drawings.
[0074] The deblocking filter 135 performs adaptive deblocking
filtering on the basis of the parameter transmitted from the filter
parameter determiner 133.
[0075] The adaptive deblocking filtering performed by the
deblocking filter 135 adjusts the filter strength by further
considering the average block edge strength, the block boundary
period, the reliability, and the block edge strength as described
above, which are not used in the conventional deblocking
filtering.
[0076] For example, the deblocking filter 135 assigns a higher
reliability to a block boundary period having a higher frequency in
the histogram described above, evaluates that a block boundary
period having a lower frequency has a lower reliability, and
adjusts the strength of the block boundary filtering according to
the reliability.
[0077] As another example, the deblocking filter 135 may adjust the
filter strength according to the local block edge strength of the
current pixel. In detail, the filter strength may be adjusted to
increase as the block edge strength is greater, and decrease as the
block edge strength is weaker.
[0078] As another example, when the block boundary period has a
large value, the deblocking filter 135 may adjust the filter size
in proportion to the block boundary size to remove blur at block
boundaries while preventing an afterimage.
[0079] The deblocking filter 135 may adjust the global filter
strength of the entire frame by calculate global statistics of the
filtering.
[0080] The deblocking filter 135 may include at least one of a
weighted average filter, a bilateral filter, or a polyphase filter
because the deblocking filter 135 varies the applied parameters
unlike in general filters.
[0081] Meanwhile, the image processor 130 may include various other
components for processing an image and modules for performing
functions. The image processor 130 may include a memory (not shown)
for storing data regarding an algorithm for controlling the
components of the display apparatus 100 or a program that
represents the algorithm, and a processor (not shown) for
performing the above described operations using the data stored in
the memory. At this time, the memory and the processor may be
implemented as separate chips.
[0082] The storage 150 may store the decompressed image and may
store various types of data, such as the determined parameters and
algorithms required for performing functions.
[0083] The storage 150 may be implemented as at least one of a
nonvolatile memory device, such as a read only memory (ROM), a
programmable ROM (PROM), an erasable programmable ROM (EPROM), an
electrically erasable programmable ROM (EEPROM), and a flash
memory; a volatile memory device, such as a random access memory
(RAM); or other storage media, such as a hard disk drive (HDD), a
CD-ROM, and the like. However, the storage 135 according to the
present disclosure is not limited thereto. The storage 135 may be
implemented a memory implemented as a chip separated from a
processor described above with regard to the image processor 130,
or may be implemented as a single chip integrated with the
processor.
[0084] The display 170 outputs an image filtered by the image
processor 130 to the user.
[0085] In detail, the display 170 for visually displaying an image
may include a display panel (not shown) and a display driver (not
shown) for driving the display panel.
[0086] The display panel outputs an image according to image data
received from the display driver. The display panel may include a
pixel serving as a unit for displaying an image. Each pixel may
receive an electrical signal representing image data and output an
optical signal corresponding to the received electrical signal. The
optical signals output by a plurality of the pixels included in the
display panel 143 are combined such that a single image is
displayed on the display panel 143.
[0087] In addition, the display panel 143 may be divided into
various types according to a method of outputting an optical signal
in each pixel. For example, the display panel may be divided into a
light emissive display that emits light by itself, a transmissive
display that blocks or transmits light emitted from a backlight and
the like, and a reflective display that reflects or absorbs light
incident from an external light source.
[0088] The display panel may be implemented using a cathode ray
tube (CRT) display, a liquid crystal display (LCD) panel, a light
emitting diode (LED) panel, an organic light emitting diode (OLED),
a plasma display panel (PDP), a field emission display (FED) panel,
and the like. However, the display panel according to the present
disclosure is not limited thereto, and may be implemented using
various display devices capable of visually displaying an image
corresponding to image data.
[0089] The display driver receives image data from the image
processor 130 and drives the display panel to display an image
corresponding to the received image data. In detail, the display
driver transmits an electrical signal corresponding to image data
to each of the plurality of pixels constituting the display
panel.
[0090] The display driver may transmit an electrical signal to each
pixel in various ways such that electrical signals are transmitted
to all the pixels constituting the display panel within a short
time. For example, according to the interlaced scanning method,
electric signals may be alternately transmitted to pixels included
in odd-numbered rows and pixels included in even-numbered rows
among all the pixels constituting the display panel. In addition,
according to the orthographic scanning method, the display driver
may sequentially transmit electrical signals to a plurality of
pixels in units of rows.
[0091] As such, when the display driver transmits an electrical
signal corresponding to image data to each pixel constituting the
display panel, each pixel outputs an optical signal corresponding
to the received electrical signal, and the optical signals output
by the respective pixels are combined such that a single image is
displayed on the display panel.
[0092] Meanwhile, the display apparatus 100 may include various
components, such as a sound output (not shown) for outputting sound
data, in addition to the above-described components.
[0093] Hereinafter, a method of controlling a display apparatus for
reducing block noise will be described in detail with reference to
the drawings.
[0094] FIG. 3 is a flowchart showing a method of controlling a
display apparatus according to an embodiment.
[0095] Referring to FIG. 3, the method of controlling the display
apparatus includes receiving an image, which is compressed and
transmitted by the image producer 10, or an image, which is
transmitted without being compressed (200).
[0096] According to an example, the image, which is decompressed by
the image receiver 110 or is decompressed and transmitted by the
image producer 10, has irregular shaped blocks as described
above.
[0097] The display apparatus 100 generates and corrects a block
boundary map for the image, which is decompressed by the image
receiver 110 or is received in a decompressed state by the image
receiver 110 (300).
[0098] In detail, the display apparatus 100 generates a first block
boundary map. The first block boundary map is generated by
normalization, convolution using a plurality of kernels, and using
a result of the convolution.
[0099] Then, the display apparatus 100 maintains boundary detected
in the first block boundary map that are continuous for a
predetermined number of pixels or more in the vertical and
horizontal directions, and excludes the remaining boundaries from
the block boundary. Then, the display apparatus 100 determines a
block period on the basis of a histogram that is generated in a
cumulative manner by integrating counts of a plurality of
inter-block intervals, and then corrects the first block boundary
map on the basis of the determined block period.
[0100] As such, the display apparatus 100 generates the first block
boundary map and modifies the first block boundary map so that a
final block boundary map is generated.
[0101] The display apparatus 100 determines a filter parameter on
the basis of information included in the finally generated block
boundary map (400).
[0102] For example, the filter parameters may be divided into a
global parameter that is based on at least one of an average block
edge strength included in the generated final block boundary map or
a reliability determined from the histogram and a local parameter
that is based on at least one of a reliability, a block boundary
period, an average block edge strength, a block boundary size, or a
block edge strength.
[0103] The display apparatus 100 performs deblocking filtering on
the basis of the determined filter parameter and the final block
boundary map (500).
[0104] The adaptive deblocking filtering according to the disclosed
example may adjust the strength of the filtering on the basis of
the determined global and local parameters.
[0105] FIG. 4 is a flowchart showing a method of generating a first
block boundary map described in FIG. 3. The method of generating a
first block boundary map will be described with reference to FIG. 4
in conjunction with FIGS. 5 to 11, which are detailed views for
describing the method shown in FIG. 4, in order to avoid
redundancy.
[0106] Referring to FIG. 4, the display apparatus 100 performs
normalization on a plurality of pixels included in the input image
(310).
[0107] Normalization may be performed through an average value of
pixels according to the number of kernel taps to be used later for
an input image. The display apparatus 100 performs normalization by
calculating differential pixels through a difference between each
pixel and the average value and dividing respective pixels by
vector magnitudes determined by the calculated differential
pixels.
[0108] Referring to FIG. 5, when the block boundary map generation
process according to the example uses a kernel having eight taps,
the normalization process may be performed by obtaining the average
of seven neighboring pixels and a pixel 180 corresponding to a
block boundary, and using a vector magnitude calculated from the
difference between each pixel and the average.
[0109] Meanwhile, the vector magnitude calculated in the
normalization process may correspond to the block edge size of the
boundary pixel 180, and may be used to determine a block boundary
period and a filter parameter.
[0110] After the normalization process, the display apparatus 100
performs convolution using a plurality of kernels (311).
[0111] The display apparatus 100 according to the embodiment
performs convolution using one or more kernels to detect irregular
block boundaries of various sizes and shapes that may be generated
due to compression.
[0112] Referring to FIGS. 6A and 6B, a block boundary generated in
a compressed image may be blurred by the upscaling or in-loop
deblocking.
[0113] The display apparatus 100 may detect block boundaries by
performing convolution using a plurality of kernels (Kernel 1,
Kernel 2, and Kernel 3) as shown in FIG. 6B.
[0114] The display apparatus 100 generates a plurality of
correlation maps on the basis of correlation values obtained
through the convolution (312).
[0115] Referring to FIG. 7, the display apparatus 100 performs
convolution on a normalized image 140 by using a first kernel
(Kernel 1, 181) in a horizontal direction 160. The display
apparatus 100 generates a first correlation map using a correlation
value obtained using the first kernel 181.
[0116] In addition, the display apparatus 100 performs convolutions
in the same direction 160 using a second kernel (kernel 2, 182) and
a third kernel (kernel 3, 183). The display apparatus 100 generates
a second correlation map using a correlation value obtained using
the second kernel 182 and generates a third correlation map using a
correlation value obtained using the third kernel 183.
[0117] Meanwhile, the shapes and number of the kernels are not
limited to those shown in FIG. 6B or FIG. 7, and may be provided in
a variety.
[0118] The display apparatus 100 selects a location of a pixel that
is equal to or greater than a predetermined first reference value
in the generated plurality of correlation maps (313).
[0119] Referring to FIG. 8, the first relevance map 160 may be
generated as a result of convolution using the first kernel 181 in
the image 140 that is subjected to a normalization process. In
detail, the first correlation map 160 may have correlation values
according to pixel locations matching with a block boundary
area.
[0120] Referring to FIG. 9, the display apparatus 100 selects a
correlation value that is equal to or greater than a predetermined
first reference value Th1 in the generated correlation map 160.
According to an example, a pixel having a correlation value equal
to or greater than the first reference value Th 1 in the first
correlation map 160 may be a pixel 180 forming a block
boundary.
[0121] The display apparatus 100 generates a block boundary map on
the basis of the pixel locations selected in the plurality of
correlation maps (314).
[0122] Referring to FIG. 10, the display apparatus 100 generates a
block boundary map 190 including the pixel 180 selected through
FIGS. 8 and 9.
[0123] Then, the display apparatus 100 repeats the above-described
processes in different horizontal and vertical directions (315), to
generate the first block boundary map 190 (316).
[0124] Accordingly, the first block boundary map 190 may be a
two-directional map of the horizontal direction and the vertical
direction.
[0125] FIG. 12 is a flowchart showing a method of correcting a
generated block boundary map. FIGS. 13A and 13B are views for
describing a method of determining a block boundary period. In
order to avoid redundancy, the following description will be made
with reference to FIGS. 12 and 13.
[0126] Referring to FIG. 12, the display apparatus 100 generates a
second block boundary map on the basis of the continuity of a block
boundary in the first block boundary map (320).
[0127] The block boundary is distinguished from a texture component
in the image and has a continuity corresponding to a block size.
Accordingly, the display apparatus 100 may identify a block
boundary on the basis of whether a boundary detected in the first
block boundary map 190 corresponds to a predetermined number of
consecutive pixels. The predetermined number of pixels may vary,
for example, according to the input image.
[0128] Meanwhile, when the continuity does not exist, the display
apparatus 100 determines the detected boundary to be a texture
component.
[0129] The display apparatus 100 generates a second block boundary
map by excluding a block boundary having consecutive pixels in a
number less than the predetermined number from the block boundary
of the first block boundary map 190.
[0130] Then, the display apparatus 100 calculates an average block
edge strength on the basis of the second block boundary map and the
histogram (321).
[0131] In detail, the display apparatus 100 accumulates a frequency
in the histogram whenever a block boundary exists at a
predetermined pixel interval in the second block boundary map.
[0132] For example, when a block boundary exists at each interval
of five pixels in the second block boundary map, the display
apparatus 100 accumulates a frequency for a fifth bin of the
histogram. After generating the histogram, the display apparatus
100 calculates the average block edge average according to the
pixel interval (a block boundary period of five pixels). In detail,
the average block edge strength is calculated by dividing the sum
of the vector magnitudes calculated at the time of generating the
first block boundary map by a period-specific frequency.
[0133] The display apparatus 100 determines a block boundary period
on the basis of the calculated average block edge strength
(322).
[0134] In detail, the display apparatus 100 compares the average
calculated block edge strength with a predetermined reference value
(a second reference value). That is, the display apparatus 100
determines a period in which the average block edge strength is
equal to or greater than the second reference value to be a block
boundary period.
[0135] FIG. 13A is a histogram showing a cumulative frequency with
respect to a block boundary period according to an example.
[0136] FIG. 13B is a graph showing the top three block boundary
periods among block boundary periods in which the average block
edge strength value calculated in each period is equal to or
greater than the second reference value (for example, 110). The top
three block boundary periods determined in the graph of FIG. 13B
are 16, 24, and 8.
[0137] According to another embodiment, the display apparatus 100
may determine a block boundary period on the basis of an offset
when a letterbox exists in the input image. That is, the display
apparatus 100 may determine the block boundary period by generating
the above described histogram while omitting an initial block
boundary of the image using a predetermined offset and then by
calculating the average block edge strength on the basis of the
histogram.
[0138] Referring again to FIG. 12, the display apparatus 100
corrects the second block boundary map on the basis of the
determined block boundary period so that a third block boundary map
is generated (323).
[0139] In detail, the display apparatus 100 maintains only a block
boundary corresponding to the determined block boundary period
while excluding the remaining block boundaries, so that a final
block boundary map (a third block boundary map) is generated.
[0140] FIGS. 14A to 14D are views illustrating a process of
detecting a block boundary according to an example, in particular,
illustrating a block boundary detection process in the vertical
direction.
[0141] Referring to FIG. 14A, an input image, after decompression,
includes a plurality of blocks. According to the disclosed
embodiment, the display apparatus 100 performs convolution using a
plurality of kernels, and then generates correlation maps on the
basis of correlation values. That is, FIG. 14B shows an example of
one of a plurality of correlation maps generated through the
above-described control method.
[0142] The display apparatus 100 generates a first block boundary
map by selecting pixel locations of pixels that are equal to or
greater than a first reference value with respect to a vertical
direction in a frame of the correlation map as shown in FIG. 14B.
That is, FIG. 14C is an example of the first block boundary
map.
[0143] The display apparatus 100 calculates an average block edge
strength on the basis of a histogram, and determines a block period
on the basis of the average block edge strength. The display
apparatus 100 may correct the first block boundary map through the
determined block period to finally generate a third block boundary
map as shown in FIG. 14D.
[0144] FIG. 15 is a detailed flowchart for describing a control
method of determining a filter parameter and performing deblocking
filtering according to an embodiment.
[0145] Referring to FIG. 15, the display apparatus 100 calculate
the average block edge strength, and evaluates the reliability of
the block boundary period from the histogram derived during
generation of the third block boundary map (410 and 420).
[0146] In detail, the display apparatus 100 may assign a higher
reliability to a block boundary period having a higher frequency
and a lower reliability to a block boundary period having a lower
frequency.
[0147] The calculated average block edge strength and reliability
may be determined to be a global parameter (450). In addition, the
evaluated reliability may be determined to be a local parameter
(460).
[0148] A block edge strength 430 and a block boundary period 440
included in the third block boundary map may be determine to be the
local parameter (460).
[0149] The display apparatus 100 performs adaptive deblocking
filtering on the basis of the determined parameters and the
generated third block boundary map (500).
[0150] In detail, the display apparatus 100 may adjust the filter
strength according to the global parameter, which is determined by
the global average block edge strength and the reliability of the
block boundary period calculated from the histogram, and also
adjust the filter strength according to the local parameter
determined by at least one of the reliability, the local block edge
strength, or the block boundary period value.
[0151] For example, the display apparatus 100 may assign a higher
reliability to a block boundary period having a higher frequency in
the histogram, evaluate that a block boundary period having a lower
frequency has a lower reliability, and adjust the block boundary
filtering strength according to the reliability.
[0152] As another example, the display apparatus 100 may adjust the
filter strength according to the local block edge strength and the
average block edge strength. In detail, the filter strength may be
adjusted to increase as the local block edge strength is great, and
decrease as the local block edge strength is weaker.
[0153] As another example, when the block boundary period has a
large value, the display apparatus 100 may adjust the filter size
in proportion to the block boundary size to remove blur at block
boundaries while preventing an afterimage.
[0154] Meanwhile, the above described adjustment of the filter
strength may be performed by individual parameters, but may be
comprehensively performed using a plurality of parameters
proportion to a predetermined coefficient.
[0155] FIGS. 16A to 16C are views for describing a block boundary
detection effect according to an embodiment, and FIGS. 17A to 17C
are views for comparing the block noise reduction according to the
disclosure.
[0156] Referring to FIG. 16, an input image is received by the
display apparatus 100. The input image decompressed by the image
receiver 110 may include irregular blocks as shown in FIG. 16A.
[0157] When the conventional deblocking filtering is performed,
only a regular block having a predetermined shape is detected.
However, the display apparatus 100 may detect various shapes of
blocks using a plurality of kernels.
[0158] FIG. 16B shows a block boundary detected in the conventional
technique, and FIG. 16C shows a block boundary detected by the
display apparatus 100 disclosed in the specification. That is, even
when an input image including an irregular block is received, the
display apparatus 100 may effectively detect the block
boundaries.
[0159] Referring to FIG. 17, the display apparatus 100 may receive
an input image having blocks as shown in FIG. 17A.
[0160] Comparing FIG. 17B with FIG. 17C shows that the display
apparatus 100 may detect block boundaries more accurately than the
conventional techniques and thus may perform deblocking filtering
in various adaptive manners, so that the block noise reduction
effect may be enhanced.
[0161] That is, FIG. 17B shows a result of filtering performed by
the conventional technique, and FIG. 17C shows a result of
filtering performed by the display apparatus 100.
[0162] As such, the display apparatus and the method of controlling
the same according to an aspect of the disclosure perform a
plurality of block noise boundary detections and generate a block
noise boundary map on the basis of a result of the detections to
cope with local block noise having irregular shapes and blurred
block boundaries, so that adaptive deblocking filtering is
performed, and block noise is reduced more efficiently than the
conventional technology.
* * * * *